Isolated BHs

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Early works

Victorij Shvartsman

«Halos around black holes» Soviet Astronomy – Astronom. Zhurn (1971)

In this paper accretion onto isolated BHs fromthe ISM was studied for different BH masses(including intermediate).

Dynamics of accretion, the role of turbulence,the role of magnetic fields in the ISM, spectrum.

Synchrotron radiation of magnetized plasma, which is heated during accretion up to 1012 K (here the temperature means the average energyof electrons motion perpendicular to magneticfield lines).

(Development of this approach see in astro-ph/0403649)

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Basic formulae

Velocity of turbulent motions

The critical velocity corresponding to an accretion disc formation.

(Fujita et al. 1998) See also A&A 381, 1000 (2002)

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Isolated accreting BHs

(Fujita et al. astro-ph/9712284)

ADAF10 solar masses

The objects mostlyemit in X-rays or IR.

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The galactic population of accreting isolated BHs

(astro-ph/9705236)

The luminosity distribution is mostly determined by theISM distribution, then – by the galactic potential.

It is important that maximaof the ISM distribution anddistribution of compact objectsroughly coincide. This resultsin relatively sharp maximum inthe luminosity distribution.

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Searching in deep surveysAgol, Kamionkowski (astro-ph/0109539) demonstrated thatsatellites like XMM or Chandra can discoverabout few dozens ofsuch sources.

However, it is verydifficult to identifyisolated accreting BHs.

(astro-ph/0109539)

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Digging in the SDSS

(Chisholm et al. astro-ph/0205138)

The idea is that the synchrotron emission can appear in theoptical range and in X-rays.

Cross-correlation between SDSSand ROSAT data resultedin 57 candidates.

ADAF IP CDAF

Regime of accretion and itsefficiency are poorly known

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Radio emission from isolated BHs

(Maccarone astro-ph/0503097)

LR ~ LX 0.7

The task for LOFAR?

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Two isolated BHs in a globular cluster?

1210.0901

eVLA observations showedtwo flat-spectrum sourceswithout X-ray or/and opticalidentfications.

Most probably, they areaccreting BHs. Probably,isolated.

Numerical model for thecluster evolution and the numberof BHs was calculated in thepaper 1211.6608.

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Electron-positron jets from isolated BHs

Barkov et al. 1209.0293

The magnetic flux, accumulated on the horizon of an IBH because of accretion of interstellar matter, allows the Blandford–Znajeck mechanism to be activated. So, electron–positron jets can be launched.Such jets are feasible electron accelerator which, in molecular clouds, allows electron energy to be boosted up to ~1 PeV.These sources can contribute both to the population of unidentified point-like sources and to the local cosmic-ray electron spectrum.The inverse Compton emission of these locally generated cosmic rays may explain the variety of gamma-ray spectra detected from nearby molecular clouds.

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New calculations for radio IBHs

1301.1341

The authors calculateif IBHs can be detectedby SKA and other futuresurvey if the accrete from the ISM.Different assumptions aboutinitial velocitites andaccretion efficiencyare made.

SKA will be effective in discovering isolated accreting BHs due to their radio emission.

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Microlensing and isolated BHs

Mao et al. astro-ph/0108312

Event OGLE-1999-BUL-32

A very long event: 641 days.

Mass estimate for the lense >4 М0

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Microlensing – the MACHO project

(Bennet et al. astro-ph/0109467)

MACHO-96-BLG-63-16 solar masses.

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Again MACHO!MACHO-98-BLG-63-13 solar masses.

(Bennet et al. astro-ph/0109467)

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Probabilities of lensing

1009.0005

30-40% of events with >100 daysare due to black holes

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The star S2 in the galactic center

(Bozza, Mancini astro-ph/0404526)

The effect is too small: 32th magnitude! (NGST?)

For a recent review on BH lensing see arXiv: 0911.2187

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Black holes around us

Black holes are formed fromvery massive stars

It is very difficult to seean isolated black hole: Microlensing Accretion …….?

It is very improtant to haveeven a very approximate idea where to serach.Let us look at our neighbouhood....

There should be about several tensof million isolated BHs in the Galaxy

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The Solar proximity

The solar vicinity is not justan average “standard” region

The Gould Belt R=300-500 pc Age: 30-50 mill. years 20-30 SN in a Myr (Grenier 2000) The Local Bubble Up 6 SN in several Myrs

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The Gould Belt Poppel (1997) R=300 – 500 pc The age is about 30-50

million years A disc-like structure with

a center 100-150 pc from the Sun

Inclined respect to thegalactic plane by ~20o

2/3 of massive starsin 600 pc from the Sunbelong to the Belt

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Close-by BHs and runaway stars 56 runaway stars

inside 750 pc (Hoogerwerf et al. 2001)

Four of them have M > 30 Msolar

Prokhorov, Popov (2002) [astro-ph/0511224]

Star Mass Velocity km/s

Age, Myr

ξ Per 33 65 1

HD 64760

25-35 31 6

ς Pup 67 62 2

λ Cep 40-65 74 4.5

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SN explosion in a binaryNormal stars

Pre-supernova

Envelope Center of mass of the system Black Hole

Optical star

Black hole

Opt. star

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ς Pup

Distance: 404-519 pc Velocity: 33-58 km/s Error box: 12o x 12o

NEGRET: 1

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ξ Per

Distance: 537-611 pc Velocity: 19-70 km/s Error box: 7o x 7o

NEGRET: 1

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Gamma-ray emission from isolated BHs

astro-ph/0007464, 0007465 – application to EGRET sources

Kerr-Newman isolated BH.

Magnetosphere. B ~ 1011 Гс

Jets.

See details about this theory in Punsly 1998, 1999.

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Runaway BHs

Approximate positions of young close-by BHs can be estimated basing on data on massive runaway stars

For two cases we obtained relatively small error boxes

For HD 64760 and for λ Cep we obtained very large error boxes (40-50o)

Several EGRET sources inside

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Resume1. Accreting stellar mass isolated BHs • They should be! And the number is huge!• But sources are very weak.• Electron-positron jets and/or radio sources• Problems with identification, if there are no data in several wavelengths

2. Microlensing on isolated stellar mass BHs• There are several good candidates• But it is necessary to find the black hole ITSELF!

3. Exotic emission mechanisms• As all other exotics: interesting, but not very probable• If it works, then GLAST will show us isolated BHs

4. Runaway stars• A rare case to make even rough estimates of parameters• Error-boxes too large for any band except gamma-rays• All hope on the exotic mechanisms (Torres et al. astro-ph/0007465)